The High Q Factor Lateral Field⁻Excited Thickness Shear Mode Film Bulk Acoustic Resonator Working in Liquid

A high Q factor film bulk acoustic resonator operating in thickness shear mode excited by a lateral field is described in this paper. The influence of electrode parameters on the resonator performance is studied by the finite element method. The results showed that three key electrode parameters, including the gap, length and width, played important roles in the optimization of the resonator performance. The highest Q factor of up to 643 was obtained when the parallel electrodes were designed to be 100 µm × 10 µm with the electrode gap of 10 µm. Based on the simulation results, the AlN-based film bulk acoustic resonator with a solidly mounted structure was fabricated. The testing results showed that the real device operated at the resonance frequency of 1.94 GHz with the Q factor of 405 in air, 216 in water and 102 in phosphate buffered saline solution.